There's a closed pull request on the void-packages repository

libmypaint: update to 1.5.0
https://github.com/void-linux/void-packages/pull/19371

Description:
Taking over for previous maintainer with permission.

Update is needed for subsequent update of mypaint package.

gimp and opentoonz link to the current library and will probably need to be updated as well. Is there some sort of proper process for this?